There are many applications in which a condition is sensed, for example, pressure of a fluid source, by a condition sensing device which provides an electrical signal upon the occurrence of a selected change in the condition; for example, a dished shaped diaphragm placed in fluid receiving relationship with a fluid pressure source to sense a change in fluid pressure. The diaphragm moves a motion transfer member when the diaphragm moves from one dished shaped configuration to an opposite dished shaped configuration with the motion transfer member applying a force to a movable contact arm, carrying a movable electrical contact, causing the movable contact to move into contact engaging relation with a stationary electrical contact to close a circuit path thereby providing an indication of the change in fluid pressure. Reliability of circuit closure is essential to ensure that the pressure indicator of the system using the pressure source operates as intended. A potential problem which can interfere with normal switch operation is for a small, e.g., microscopic, particulate contamination to find its way on the surface of the contacts at the point of engagement thereby preventing electrical closure of the circuit path even though the contacts have moved into physical engagement with one another. Although the problem normally occurs very rarely, for example, on the order of about 100 ppm, i.e., a 1 in 10,000 probability, this is considered to be unsatisfactory with regard to present day manufacturing standards where zero ppm is the goal.
In order to improve reliability, it is known to provide switches having multiple contact wipers, i.e., essentially a plurality of movable contact arms acting in electrical parallel, wherein the probability of having at least one contact wiper free of contaminants is essentially infinite; however, typically this involves some type of mechanical and electrical interconnection structure as well as a means for providing sufficient force to actuate the multiple wipers. This may be suitable for a more expensive and larger electrical switching systems but is not suitable in low cost indicator switches.